不同工业企业周围土壤-作物系统重金属Pb、Cd的空间变异及其迁移规律

Spatial variability and transfer of Pb and Cd in soil-crop system around different types of factories

摘要:

对苏南不同排污方式的3个工业企业周围土壤-作物系统的重金属空间变异、迁移及影响因素进行了深入研究。研究表明：污水排放分别导致了氧化铅厂（F1）和化工厂（F2）周围农田土壤中Pb和Cd的聚集，其上作物的重金属吸收量也明显提高。而以大气排放为主的冶金企业（F3）导致土壤中重金属的轻微积累，也显著提高了作物中Pb的含量。在空间分布上，污水排放企业周围土壤和作物重金属的强烈聚集区出现在企业排污口附近约50 m范围内，并随着距企业距离的增加重金属含量呈指数降低，高于土壤背景值的污染范围分别为400 m（F1）和100 m（F2）。进入土壤的Pb和Cd主要聚集在土壤表层0～20 cm范围内。在企业污水灌溉的影响下，水稻Pb和土壤Pb、水稻Cd和土壤Cd均呈显著的指数关系；小麦Cd和土壤Cd呈显著的线性关系。当小麦和水稻Cd含量超过国家食品卫生标准（0.2 mg kg^-1）时，土壤中有效Cd含量分别为0.360 mg kg^-1 和0.319 mg kg^-1，全Cd分别为1.50 mg kg^-1 和1.42 mg kg^-1。而在大气污染的影响下，土壤-作物中的重金属无明显的相关性．

Abstract:

Study was carried out on spatial variability and transfer of heavy metals and their driving factors in cropsoil systems around three different types of factories in southern part of Jiangsu Province. Results show that wastewater irrigation led to Pb and Cd accumulation in soils around F1 (a lead oxide factory) and F2 (a chemical factory), respectively, and concentrations of heavy metals in crops were also increased. Although F3 (a metallurgical plant) did not cause any significant heavy metal accumulation in the soils around, its waste gas emission greatly raised Pb concentration in the crops. Spatially soils and plants high in heavy metal concentration were distributed maily within the radius of about 50 m from the waste water outlet, and decreased exponentially with the distance from the factory. Soil with heavy metal contents higher than the local soil background values were found within the radius of about 400 m (F1) and 100 m (F2). In soil profile, Pb and Cd were accumulated mainly in 0～20 cm soil layer. Affected by wastewater irrigation, there were significant exponential relationship between Pb in rice and Pb in soil and between Cd in rice and Cd in soil, and significant linear relationship between Cd in wheat and Cd in soil When soil available Cd and total Cd in the soil was 0.319 mg kg^-1 and 1.42 mg kg^-1, respectively, Cd concentration in wheat would exceed the criterion of the national food safety standard (0.2 mg kg^-1); and when soil available Cd and total Cd in soil reached 0.360 mg kg^-1 and 1.50 mg kg^-1, respectively, Cd concentration in rice would exceed the criterion. Under the air pollution, no significant relationship was found between the heavy metal in crops and in soil.